I use a large cutter on mine. They can be done with separate petals for a bigger rose.
I made roses for the first time for a cake this past weekend. I got to finally use a large cutter I purchased online a while back!
For large roses, I use larger cutters and wire the petals. I pull back the edges and dry them on a ring made from twisting kitchen paper ( cheaper than buying a former). Then attach them to the rose when they are dry. HTH